1. Field of the Invention:
This invention relates to an image scanner for giving image data to an image processing device such as a word-processor or a computer to effect image processing, and more particularly to a portable scanner having a peep hole through which an image portion to be read on a given objective image plane can easily be observed, but external light affecting the reading of the objective image is little allowed to pass.
2. Description of the Prior art:
There have been proposed various types of image scanners or image readers in recent use, which are adapted to scan over a given objective image plane such as a picture or printed matter so as to read out image information from the image plane and output image data to an image processing device such as a computer or word-processor for the purpose of image processing. Among these conventional image scanners is one called a portable image scanner. Generally, the portable image scanner is composed of, as fundamental elements, a light source for illuminating a reading portion to be read on the objective image plane, an image sensor for converting optical image information read from the objective image plane into electric image signals, and an optical system including a converging lens for introducing reflected light from the objective image plane into the image sensor. Some of the conventional portable image scanners have a viewing structure for allowing the reading portion on the objective image plane to be observed with the eye for positional confirmation, which reading portion is closed to the view by the scanner proper, as disclosed in Japanese Patent Publication SHO No. 45(1970)-13858; Japanese Utility Model Publication SHO No. 54(1979)-7719; and Japanese Utility Model Application Public Disclosures SHO No. 51(1976)-81035(A); SHO No. 55(1980)-14694(A); SHO No. 57(1982)-185063(A); SHO No. 60(1985)-170866(A); and SHO No. 61(1986)-176857(A). The viewing structure in any of the aforesaid conventional image scanners is adapted to facilitate proper positioning of the scanner for scanning the given objective image plane. However, the conventional portable image scanners cannot exactly adjust the reader part of the scanner at a desired reading position to be read on the objective image plane and have a disadvantageous factor causing the accuracy of the image reading to be decreased.
To be specific, in FIG. 1, there is shown one example of the prior art image scanners, which has a viewing window W formed right above the reading portion P on a given objective image plane I between a light source L and an image sensor S. Through the viewing window W, ambient light enters inside the scanner body and is scattered on the image plane I. The scattered light is mingled as noise component in a desired image light reflected from the objective image plane I. As a result, the image sensor S receives the desired image light interfered with the undesirable scattered light brought about by the external light. Thus, the light is influenced by the external light, with the result that the quality of a reproduced image obtained by an image processing device such as a computer is remarkably decreased. Moreover, since the light source L and the image sensor S are positioned symmetrically with each other about the reading portion P, when the objective image plane to be read is glossy, the image plane glares under illumination of the light source L, thereby to make it difficult or impossible to reliably read out the image from the objective image plane. Besides, since the objective image plane is read sideways by the image sensor, the reproduced image obtained by the image processing device is apt to be distorted.
In a prior art image scanner as illustrated schematically in FIG. 2, a semi-permeable reflecting means (half mirror) R is interposed in a light path extending from the reading portion P on an objective image plane I to the image sensor S, so that an operator can observe the reading portion P for positional confirmation through the reflecting means R. However, the desired image light reflected from the objective image plane I is attenuated to lower the luminescent efficiency due to the semi-permeable reflecting means R.
There has been need for a handy image scanner which permits the viewing of the reading portion on the objective image plane to be performed more easily in a reading operation and can be handled with ease.